Abstract
The jacket platform in the Bohai Sea oilfield is an important engineering development, offering design alternatives in this economically important region. However, ice-induced vibration in cold areas threatens the safety and operation of these platforms. On two occasions, intense ice-induced vibrations triggered the rupture of a well’s blow down pipeline, loosening the flanges on the Bohai platform, and leading to the ejection of high-pressure natural gas. Subsequent mechanical analysis of the failed parts helped define the mechanism of failure and identified the failure criteria, based on a prototype structure monitoring system. The analysis revealed that the deck’s inertial force, which resulted in ice-induced steady-state vibration, was the major cause of the accident. Three fixed cones were thus installed on the platform the following winter, effectively reducing the vibrations.
Highlights
The shallow waters of the Bohai Sea are home to an abundance of oil reserves
This paper addresses the ice-induced vibration risk of oil and gas exploration in the Bohai Sea through a case study of the pipeline and flange failure that occurred in Liaodong Bay
Based on the failure analysis of topside facilities on oil/gas platforms in the Bohai Sea, this paper recommends that the following criteria be considered for future design and risk assessment studies:
Summary
The shallow waters of the Bohai Sea are home to an abundance of oil reserves. More than 100 offshore platforms have been built on this gulf, making it the second-largest offshore oil production base in China. Owing to the specific characteristics of marginal oilfields, the Bohai Sea oil and gas platform is an economically important jacket structure, to which the threat from sea ice is far greater than environmental hazards (wind, waves, currents, tides, earthquakes, etc.). This paper discusses two serious accidents that took place on a Bohai platform, caused by intense ice-induced vibration. TTThhhiiisss pppaaapppeeerrr aaaddddddrrreeesssssseeesss ttthhheee rrriiissskkk ooofff oooiiilll aaannnddd gggaaasss eeexxxppplllooorrraaatttiiiooonnn iiinnn ttthhheee BBBooohhhaaaiii SSSeeeaaa ddduuurrriiinnnggg wwwiiinnnttteeerrr. The following conclusions were made by analyzing the macro- and micro characteristics of the fracture: The fracture of the blowdown pipe had obvious fatigue features, and it exemplified a low-cycle fatigue fracture under a bending load. The severe iceinduced vibration accelerated the fatigue failure of the blowdown pipe and eventually caused the ejection of high-pressure naFtiugurarel g5.aTs.he fractured edge of the blowdown pipe.
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